Method of obtaining concentrates from weak solutions



Patented June 2;, 1948 MET-HOD OF OBTAINING CONCENTRATES FROM WEAKSOLUTIONS Harry A. Noyes, WatertowmMass.

No "Drawing.

Original application August 26,

' 1940, Serial No. 354,253. Divided and this application May 26, 1945,Serial No. 596,093

13 Claims.

- The present invention relates to the production of concentrates andprecipitates from plant juices, extracts, and infusions. Its objects areto obtain such concentrates and precipitates by the use ofrefrigeration; to refine and clarify such substances through utilizing"the consequences of "solubility products phenomena existing'attemperatures below the freezing point of water; to obtain the desiredsubstances by adding miscible materials which lower the freezing pointsof solutions having low contents of solids and subsequently effectingiceseparation through controlled extraction and addition of heat; and toemploy the controlled formation of ice as a means of concentrationand/or separation of soluble or insoluble matter present in solutions.

The present application in which the procedures for realizing theforegoing objects are described and claimed is -a division of my. priorapplication Serial No. 354,253, filed August26, 1940 (on which Patent2,395,498 was issued February 26, 1946), entitled Treating plantproducts. Plants and the natural products of plants are the sources ofdrugs and other compounds having specific medicinal values and otherqualities prized for various reasons by mankind. ,Such compounds andsubstances, whennot existing exclusively in the juice of the plant orits fruit, are extracted in various ways by theyuse of water, alcoholand other solvents or. liquid vehicles which are capable of extractingthe substances.

Many of the aqueous solutions obtained by percolation or otherprocedures in which water is used as a solvent, are weak in the totalquantity of solids present in solution and their freezing points are notappreciably lower than the freezing point of pure water. Many of thesubstances herein referred to are not soluble in water in large enoughquantities to make solutions of which the freezing points areappreciably lower than that of water. Hence when heat is extracted fromsuch solutions to the extent that the solvent is changed to the solidstate, the dissolved matter is not susceptible of being advantageouslyseparated by controlled addition of heat to the mass.

The present invention comprises treatments by which weak solutions areconditioned for concentration of specific soluble solids therein andondary solution may be pared to have a freezing point of 30 F. or lower;

also an aqueous one prethat is, preferably two degrees or more below thefreezing point of the solution to be concentrated.

The freezing point depressant in the secondary solution may be a solublesolid or a liquid of which the freezing point is lower than that ofwater, which can be separated from the desired substance by suitablefurther treatment, or is such that its presence in admixture with thesubstance is desired or. unobjectionable.

point and/or heat is further extracted until a considerable quantity ofice'crystals vform in it.

separation of the specific soluble solids therefrom.

The solution to be concentrated is cooled to approximately its freezingpoint, but not enough to freeze it, and is then gradually added to themixture of the secondary solution and ice. Heat is withdrawn from themixture as the solution to be concentrated is added, so as to maintainconditions for increased ice separation, and the solu-j tion is kept inmotion in a manner such that the energy applied in moving it does notgenerate enough heat to prevent the desired ice formation. Under thisprocedure, water in'the solution to be concentrated crystallizes as iceon the ice already present and/or forms new ice without entrapping anyconsiderable proportion of the matter dissolved in the original juice orinfusion Thereby the infusion is concentrated. When concentrated to thedesired degree, it is removed from the ice.

When the desired product is one which is put out for use in preparationscontaining alcohol, sugar, glycerine, or other soluble or misciblesubstance of which the freezing point is lower than that of water, thesecondary solution above described is often made up with one or more ofsuch substances in concentration suflicient to lower its I freezingpoint to the desired degree.

A variation of the procedure which may be used is to extract heat fromthe secondary solution until such capacity for absorption of heat beconcentrated is an aqueous solution, the sec- M (ore described may becarried to the point where 3 r the desired ingredients are precipitatedas solids, which are collected therefrom in the solid state.

Another variation is to make the temperature of the secondary solutioncontaining ice crystals suchthat the ice present tends to melt, then adda small amount of the plant juice orextract to the solution, extractheat from the resulting mixture to the degree where ice formationresults, proceeding thus until enough ice has separated to causeconsiderable concentration of the liquid remainder of the solution, thenadding more of the liquid to be concentrated, and continuing until adesired concentration has been achieved.

When the residual solution has been thus concentrated to the extent thatits freezing point is appreciably lower than that of water, extractionof heat may be continued until the whole mess is virtually solid, thatis, brought to the condition where the properties of a liqmicease to beevident in the frozen mass. Thereafter heat is applied to the virtuallysolidified mass, not at a high temperature, but at a temperature, lowerthan the freezing point of water, at which a concentrated solution ofthe substance to be re-' covered is liquefied. The heat is applied insuch manner that it is well distributed throughout the solid mass andequally effective, or substantially so, on the mass as a whole. Thisliquid concentrate is then separated from the ice mass.

Some of the substances contained in extracts of the character herereferred to are insoluble in highly concentrated solvents, such asalcohol, while being soluble in dilutions of the same s01- vents. Forrecovering such a substance, a dilute secondary solution of such solventis made, chilled, and mixed with the plant extract in any of the modesprecedently described. Separate formation of ice then produced resultsin causing increased concentration of the alcohol (or other solvent) aswell as of the matter in solution, until the latter is precipitated. Or,if desired, a. quantity of the concentrated solvent may be added eitherbefore or when the ice formation has proceeded to the extent aboveindicated.

The liquid solution is then drained off through the ice particles,leaving the ice and the pre-- cipitate entrapped among the ice crystals.

In this, and other of the within described procedures where the materialwhich it is desired away from the ice with the solution can be separatedby other filtering means.

It is necessary to keep the mixtures of solutions herein described attemperatures lower than those at which there would bean equilibriumbetween the ice phase and water. Since glycerine, sugars and some othertemperature depressants tend to delay the formation of ice, theirspecific retarding effects in some cases must be overcome by theemployment of temperatures lower than the freezing points calculated onthe basis of the amounts of the substances present, and sometimes byagitation.

phase of the solvent is produced without solidiilcation of the entirequantity of solution.

In carrying out any of the foregoing procedures the addition of thesolution from which the water is to be separated as -ice must be soregulated that it is not quick frozen" "en messe" before there isseparation of the constituents.

I have discovered that the mechanics of the solution can be differentJust as soon as some other substance besides ice is coming out ofsolution on the further extraction of heat. If, for

example, lactose is present, in solid form, and in solution, and thereis ice also, I have noted a tendency for the lactose that is out ofsolution to go into solution with a very limited but temporaryprevention of further formation of ice when water is added forseparation by the temperature lowering step. Within close ranges, theheat of solution, latent heat of melting, and the production of acondition that gives a new phase of a substance all have influences thatmust be taken into account in connection with the extraction of heat,according as the phenomena are endothermic or exothermic.

What I claim is:

1. The method of concentrating plant juices, extracts and infusions,which comprises providing a secondary solution of which the freezingpoint is lower than that of the solution to be concentrated and which ismiscible therewith, chilling such secondary solution to its freezingpoint, cooling the solution to be concentrated to a temperature near itsfreezing point, and mingling the two solutions while withdrawing heattherefrom, so that part of the solvent of the first solution istransformed to the solid phase.

2. The method of concentratin plant juices, extracts and infusions ofwhich the freezing point is approximately the same as that of purewater, which comprises chilling a secondary solution, which is misciblewith'the solution to be concentrated and of which the freezing point islower than that of water, until crystals form therein, cooling thesolution to be concentrated to near its freezing point, and adding it tothe secondary solution, with subsequent extraction of heat from thelatter, at a rate such that a portion of the water content of-the firstsolution freezes on the ice crystals of the secondary solution.

' 3. The method of concentrating plant iuics, extracts and infusions,which comprises preparing a solution of a substance which is misciblewith the solution to be concentrated and of which the freezing point islower than that of water, chilling the secondary solution to atemperature lower than the freezing point of water, and adding saidchilled solution to the first solution in quantity sufiicient to causeformation and accumulation of ice therein.

4. The method of concentration set forth in claim 1, combined with thefurther step of sapcrating the ice so formedfrom the residual liq- 5.I'he method according to claim 2, combined with the step of separatingthe ice so formed from the residual liquid.

tialiy lower than the freezing point of water,

chilling a quantity of the second named solution to a temperaturesubstantially lower than the freezing point of water, and mixing the twosolutions together in proportions such that water in the plant extractsolution is converted into ice and the plant extract is precipitated.

8. The method of obtaining in concentrated form a plant extract which issoluble in a given solvent when the solvent is diluted with water but isinsoluble in the concentrated solvent, which consists in preparing adilute water solution of such solvent having a freezing point lower thanthe freezing point of water, mingling that solution with the aqueousplant extract solution, and withdrawing heat from the mixed solutionsuntil a substantial proportion of the water in the mixed solutions istransformed into ice and the residual solution is concentrated to thedegree of solvent strength at which the plant extract in solution isprecipitated.

9. The method of obtaining in concentrated -form from an aqueoussolution thereof a plant extract which is soluble in alcohol and-watersolutions of relatively low alcohol content and insoluble in suchsolutions of high alcoholic strength, which comprises extracting heatfrom a dilute alcohol solution of such plant extract insufficientmeasure to cause transformation ofi so much of the water content of thesolution into ice that the alcohol content thereof is concentrated tothe extent that at least part of the extract is precipitated, andseparating the resid ual liquid and precipitate from the ice.

10. The method of obtaining in concentrated form from an aqueoussolution thereof a plant extract which is soluble in alcohol and watersolutions of relatively low alcohol content and 6 liquid from the ice soformed in a manner to cause deposition of precipitate on the ice, andrecovering the precipitate by melting the ice and separating the waterof liquefaction from the precipitate.

11. The method of obtaining in concentrated form a plant extract whichis soluble in wateralcohol' solutions of relatively low alcohol contentand insoluble in such solutions of high alcoholic strength, whichcomprises withdrawing heat from a dilute alcohol solution of such plantextract until a substantial proportion of the water content thereof istransformed into ice, and then adding suillcient alcohol to the solutionto precipitate the extract.

12. The method of obtaining in concentrated form a plant extract whichis soluble in waterinsoluble in such solutions of high alcoholicstrength. which comprises extracting heat from a dilute alcohol solutionof'such plant extract in suflicient measure to cause transformation ofso much of the water content of the solution into ice that the alcoholcontent thereof is concentrated to the extent that at least part of theextract is precipitated, withdrawing the residu l alcohol solutions-ofrelatively low alcohol content and insoluble in such solutions of highalcoholic strength, which comprises withdrawing heat from a dilutealcohol solution of such plant extract until a substantial proportion ofthe water content thereof is transformed into ice, then adding ufficientalcohol to the solution to precipitate the extract, withdrawing theresidual liquid from the ice in such manner that precipitate isdepositedon.the.ice,melting the ice, and separating the water ofliquefaction from the precipitate.

13. The method of obtaining in concentrated form, from a dilute aqueoussolution thereof, a plant extract which is soluble in an alcohol andwater solution but insoluble in concentrated al cohol, which comprisesmingling the aqueous solution of the plant extract with an aqueoussolution of alcohol having a freezing point lower than the freezingpoint of water, and extracting heat from the mixture in sufllcientmeasure to cause transformation of so much of the water content of themixture into ice as to concentrate the alcohol content thereof to theextent that at least part of the extract is precipitated.

I HARRY A. NOYES.

I REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATE 'rli'rnu'rs Number Name Date 761,387 Monti May 31, 19041,362,870 Johnson Dec. 21, 1920 1,879,470 Monti May 24, 1021

